Butterflies at home in the Wood

I was out with my machete and gardening gloves attacking briars and nettles that were threatening to engulf the young trees and shrubs I had planted in the wilder end of my garden. I call this end of the garden The Wood, which is a little grandiose because it’s too small to be a real wood.

However, it does have some fairly substantial ash, oak and hazel in it and, on a sunny day, there is wonderful dappled light there. The light and dark patches on the ground are in constant movement as the breeze moves the leaves above.

Then I was distracted from my work by a butterfly fight. Two fast-flying, medium-sized butterflies flew round each other in tight spirals and drifted sideways on the breeze as the combat developed. Then one of them broke away and fled and the victor settled close to me in a patch of sunlight to get its breath back.

A dark brown butterfly with an irregular pattern of cream spots and blotches on its wings. A speckled wood. A well-named butterfly because it loves dappled woodland. It was a male. I knew this because only the males indulge in these territorial fights and because females are larger and have larger cream spots. They are far and away the commonest butterfly in The Wood.

Males have two separate strategies for finding a mate. One is to patrol up and down a fiercely defended territory, though usually only when the sun is shining. The other is to lie in wait on a fence post, a rock or a leaf until a female flies past.

They are the most shade-tolerant of all our butterflies but they are absent from really dense woodland — they seem to need that dappled effect when some sunlight reaches the woodland floor. In fact, in these sort of light conditions they are well camouflaged, the cream is the colour of the sunlight and the background dark brown of the shaded parts of the woodland floor.

Speckled woods seldom visit flowers to gather nectar. I have occasionally seen them alight on heads of cow parsley or wild carrot but they may have been just perching rather than feeding. Instead they eat the honey-dew produced by aphids. Aphids are sap suckers and much of the sap they suck contains more sugars than they can metabolise. The surplus sugars are excreted as ‘honey-dew’, a substance that is very energy-rich.

Surprisingly the larval food plant of this woodland butterfly is not a tree but a grass. Or rather, several species of the sort of long grass that grows in woodland glades and margins. Cock’s foot and couch grass are the two commonest species. There are normally three broods in the year and the caterpillars and the chrysalises are grass-coloured. They over-winter as either a larva or a pupa with a first brood of winged adults appearing by April.